The present invention relates to liquid ejection apparatuses.
Typically, an electro-optic apparatus such as a liquid crystal display and an organic electroluminescence display (an organic EL display) includes a plurality of electro-optic elements formed on a substrate. An identification code or a product number is marked on the substrate for the sake of quality control and product control. The identification code is defined by a two-dimensional code that represents the product number of the substrate. The identification code is readable and decoded by a specific code reader, or an identifying member.
In order to mark an identification code on a substrate, a metal-foiled film may be arranged to be opposed to the substrate (which is defined by a glass substrate). Laser radiation is then performed so as to transfer a metal film onto the substrate, thus marking the identification code on the substrate. Alternatively, water containing abrasive may be ejected onto the substrate in such a manner as to mark a numeral on the substrate. For more detailed information, refer to Japanese Laid-Open Patent Publication Nos. 11-77340 and 2003-127537.
However, the aforementioned code marking methods each include a number of steps and need an expensive and large-scaled apparatus. Thus, to avoid these problems, an inkjet method has been considered as an alternative to the conventional methods. The inkjet method is performed by a relatively small-scaled apparatus and shortens the time needed for forming an identification code. More specifically, the inkjet method involves use of a liquid ejection apparatus that ejects functional liquid (ink droplets) onto a substrate through nozzles. This forms the identification code, which is defined by a two-dimensional bar code or the like, on the substrate.
Japanese Laid-Open Patent Publication No. 5-309835, for example, describes a technique for easily mass-producing inkjet type liquid ejection heads that increase ejection density and improve ejection accuracy. More specifically, patterning is performed on a silicon wafer of (110) plane orientation. Bores are then defined in prescribed portions of the wafer. Subsequently, crystal anisotropic etching is performed on the wafer. This forms-a liquid ejection head including ink nozzle bores, each of which is defined by (111) planes perpendicular to a surface of the wafer, provided integrally with ink pressure chambers.
Further, Japanese Laid-Open Patent Publication No. 6-23980, for example, describes a technique related to an inkjet recording apparatus having a configuration that improves efficiencies for performing mass-production and conducting tests. In this inkjet recording apparatus, ejection performance of a liquid ejection head is estimated simply and efficiently using an optical power meter. The liquid ejection head includes separate ejection chambers, oscillation plates, drive portions, and a common ink cavity. Each of the ejection chambers communicates with a corresponding nozzle bore. Each of the oscillation plates defines a wall portion of the associated ejection chamber and is driven by the corresponding drive portion. The ink cavity supplies ink to each ejection chamber. A transparent electrode substrate is arranged below the oscillation plates and includes an electrode formed by a transparent conductive film. The interior of the liquid ejection head is thus visible from the exterior.
The inkjet method for forming the identification code involves an ejection step and a drying and baking step. In the ejection step, ink droplets are accurately ejected onto desired portions of the substrate. In the drying and baking step, the droplets are dried on the substrate and the functional material of the ink is baked and thus securely bonded with the substrate.
In order to accurately supply the ink droplets to the desired portions of the substrate, the substrate must be arranged close to the liquid ejection head. If the standby period between ejection and drying is excessively long, the droplets may spread or contract in a wet state. To prevent this, it is necessary to perform the dying and baking steps quickly and efficiently following the ejection step. However, since the substrate and the liquid ejection head are located close to each other, the portions of the substrate that have received the droplets are shielded by the liquid ejection head. Thus, the drying step, which involves laser radiation, must be delayed until the droplets that have been received by the substrate become exposed. Such delay may make it impossible to maintain an appropriate shape of each droplet. To avoid this problem, a transparent substrate stage may be employed if the substrate is transparent. The laser radiation is thus performed through the backside of the substrate, which is mounted on the substrate stage. However, this option is applicable only to the transparent substrates.